Republican presidential candidates former Pennsylvania Sen. Rick Santorum, former Massachusetts Gov. Mitt Romney and former House Speaker Newt Gingrich shake hands before the start of the South Carolina Republican debate at the North Charleston Coliseum in Charleston, S.C., Thursday.

But this time around, proponents of regime change envision not a boots-on-the-ground war but ever-tightening economic sanctions as the preferred means of toppling what many in the US view as an outlaw leadership.

Sanctions, primarily a cut-off of Iran’s oil income, would cause such disarray and social unrest, the thinking goes, that the Iranian people would rise up and do away with the root cause of the Iranian crisis, the country’s leaders.

Others scoff at the idea of an externally induced revolution as wishful thinking, but say the rise of regime change rhetoric reflects the climate of a post-Iraq US election year where everyone wants to sound tough on Iran without endorsing an Iraq-style solution.

The idea that regime change is the only viable and lasting solution to the challenges posed by Iran – its advancing nuclear program, its sharpened brinkmanship over the Strait of Hormuz, its support for Islamist extremist movements around the world – has received growing attention and support from Republican presidential candidates vying to out-tough one another on Iran policy.

Former House Speaker Newt Gingrich is the most vocal proponent of the “It’s the regime, stupid,” position, advocating regime change in foreign-policy debates and elaborating on how he would accomplish the goal: by “cutting off the gasoline supply to Iran and then, frankly, sabotaging the only refinery they have.”

For some experts, Iran must take some responsibility for fomenting the shift in the Iran discussion. “Iran has done its part to encourage the regime-change talk by brandishing the threat to close the Strait of Hormuz,” says Christopher Preble, vice president for defense and foreign policy studies at the Cato Institute in Washington.

The Obama administration is also playing a role by using expressions like “tightening the noose” to describe what stronger sanctions are designed to do to Iran, some Iran experts say.

Adding to the frenzy is recent US legislation that targets any country, friend or foe, that continues to purchase Iranian oil through Iran’s central bank, and a proposed European Union (EU) embargo on imports of Iranian oil that could be approved as early as Monday.

An EU embargo on Iranian oil would represent a significant step, since Europe buys about 20 percent of Iran’s oil. European officials say the move may be the last option for forcing Tehran to “change course” before military action, which the Europeans want to avoid.

“If we want to avoid this dilemma of either the Iranian bomb or bombing Iran, then we have to go very far to force them to change course,” says one senior European diplomat in Washington.

The Europeans are not talking about regime change, but their new toughness is boosting those in the US who believe seriously toughened sanctions could be the key to what they say should be the goal: toppling the Iranian regime.

Taking a cue from the Arab Spring and the toppling of Arab tyrants by popular movements, some regional experts say an Iranian population infuriated by increasingly dire economic conditions could do the same. A “tsunami of sanctions” could be implemented “in a way that gives rise to the sort of popular economic discontent that led to the uprisings in the Arab world a year ago,” write two specialists with Washington’s Foundation for Defense of Democracies, Reuel Marc Gerecht and Mark Dubowitz, in a recent Bloomberg opinion piece.

Others say sanctions alone won’t work, no matter how tough they are. John Bolton, the former US ambassador to the United Nations, is all for regime change in Iran but he says induced economic hardship won’t do it: Iran has too many high-powered friends – Russia and China to start with – and he points to North Korea, which he says has preferred to starve its own population rather than give up its nuclear stockpile.

Still other experts say regime change is not the magic formula for preempting a nuclear Iran, since the Iranian population shows every sign of supporting the country’s nuclear program.

The journalist and author Robert Wright, writing in the Atlantic, notes that polls have shown that strong majorities of Iran’s Greens, who took to the streets to protest the 2009 elections, and other pro-opposition segments of the population are adamant that Iran should not give up its nuclear program “regardless of the circumstances.”

Further noting that the Iraqi government that has resulted from a regime-change war can hardly be accused of “hew[ing] to our policy guidelines,” Mr. Wright adds that, “when you induce regime change by tightening sanctions to the choking point, you don’t get to micro-manage the transition.”

That may be true, but the premise of the regime-changers seems to be that, just as Iraq’s government today, even if not exactly what the US would choose, is better than Saddam Hussein, so would a post-mullahs Iranian government almost certainly be preferable to what now rules in Tehran.

General Hayden, who places Iran at the top of his “list of five things to worry about,” says Iran earns that ranking not simply because of its nuclear program but because of the threat nuclear proliferation poses and because of the Iranian regime’s track record (of sponsoring international terrorism, for example).

Speaking Thursday at a discussion sponsored by Washington’s Center for the National Interest, Hayden said Iran can be seen to be operating under two clocks: one the nuclear clock, which sanctions aim to slow down, and another clock determining the pace of political change in Iran.

Hayden said he’d like to be able to turn back the second clock to June 2009, the height of Iran’s aborted “green revolution,” to see “where that might have led.”

The objective is to “slow down one clock long enough to allow the other to catch up,” Hayden says. “If you can slow it down long enough, maybe the direction of Iran changes.”

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Watch this video on key issues on the minds of social conservative or values voters in South Carolina.